Exhaust gas systems for motor vehicles include, for example, heat exchangers in order to be able to utilise the heat of the exhaust gas originating from the internal combustion engine. The exhaust gas flows from the internal combustion engine through the heat exchanger and transfers the heat thereto, for example for pre-heating media, in order to achieve a more rapid heating of the engine, or for heating the passenger compartment.
The exhaust gas originating from the combustion engine can, as a function of the required heat output of the heat exchanger, flow through or be guided past the heat exchanger.
The exhaust gas heat exchanger is connected to the exhaust gas pipe, for example, using a valve assembly. The valve assembly includes two inlets as well as two outlets and the exhaust gas pipe is connected to a first inlet and a first outlet. The heat exchanger is connected to a second inlet and to a second outlet. In the valve assembly, a closure element is provided which in a by-pass position opens the first flow path and closes the second flow path and/or the third flow path, and in a normal position closes the first flow path and opens the second flow path as well as the third flow path. In the by-pass position, the exhaust gas can be guided past the exhaust gas heat exchanger without flowing through it. In the normal position, the exhaust gas flows at least partially through the exhaust gas heat exchanger.
However, in order to actuate the closure element, great operating forces are required, because the closure element has to be moved against the flow of the exhaust gas into the normal position and has to be kept there. Moreover, in the case of the valve assemblies known so far, an undesired pressure differential or turbulence may occur on the closure element of the valve assembly.